During a telephone call between a mobile telephone handset and another telephone, the mobile telephone handset may cross from the domain of one wireless network to an independent wireless network. In the absence of a connection transfer procedure, the telephone call will be dropped and communication can be re-established only by making a new telephone call.
In the prior art, handover of a telephone call from the domain of a first wireless network to a domain of a second wireless network is made if a control link is shared between central processing units (for example, switches) of the two networks. Using the control link, the two wireless networks are able to negotiate feasibility and operations of handover, see, for example, EIA/TIA Interim Standard IS-41.2-B, "Cellular Radiotelecommunications Intersystem Operations: Intersystem Handoff."
The above-described approach is disadvantageous in that it requires a control link between central processing units, i.e., switches, of the networks. Although switches supporting adjacent geographical areas may share such a control link, two switches supporting overlapping areas are likely to be owned by competitors and, as a result, will not share a control link. In particular, public Personal Communications Services ("PCS") and private wireless networks will not share such a control link; nor will competing Cellular service providers share such a control link.
In light of the above, there is a need in the art for a method which provides continuation or connection transfer of an ongoing telephone call during a mobile telephone handset's transition from one wireless network to another, for example, connection transfer from a private wireless network (Wireless Private Branch Exchange ("W-PBX")) to a public wireless network (Personal Communications Services ("PCS"), or vice versa.